But the mayor of Anderlecht, an area of the Brussels region, told Belgian radio there was a serious risk to public safety because protesters were thought to be planning to take to the streets against the congress.

The Belgian League against anti-Semitism filed a complaint with the Brussels prosecutor on Friday, condemning "a veritable day of hate".

On Saturday, 19 mayors from the Brussels region met police chiefs to assess the planned meeting.

Writing on his Facebook page, Laurent Louis said it was laughable that his movement "Debout Les Belges!" (Stand up, Belgians!) was seen as anti-Semitic, simply because its members had adopted Dieudonne's trademark "quenelle" gesture.

Described as an inverted Nazi salute, the quenelle is claimed by Dieudonne to be an anti-establishment symbol.

Earlier this year, French footballer Nicolas Anelka was fined and banned by the Football Association for using the sign during a televised match. An independent FA panel decided the gesture was "strongly associated with anti-Semitism".